China’s Sinovac vaccine has been found to be 50.4% effective in Brazilian clinical trials, significantly less effective than initial data released, according to reports by researchers.
Butantan Institute, the public institute based at São Paulo completed the late-stage trial of the vaccine CoronaVac. However, the institute has been criticised by scientists and health experts for releasing partial data that generated unrealistic expectations damaging the credibility of the vaccine.
The institute delayed three times in releasing the trial result due to the confidentiality clause in its contract with Sinovoc.
According to Butantan, the CoronaVac was 78% effective among volunteers with mild to severe infections. However, the institute announced again that the overall potency dropped to 50.4% when including “very mild” cases that did not require medical assistance.
US-based Covid vaccine Pfizer-BioTech and Moderna have shown a 95% effective rate in the phase three trial.
Other than Brazil, countries such as Turkey and Indonesia are also conducting trials on the Covid-19 vaccine.